The present invention relates to a disk-shaped storage medium on or from which data is recorded or reproduced using a laser beam, and to a tracking method using the disk-shaped storage medium.
Recently, as disk-shaped storage media, optical disks have been put into practical use as large capacity data files and media for storing music or images. However, it further is intended to increase the capacities of such disk-shaped storage media so that they can be applied in more various uses. For efficient access to a large capacity optical disk, the following method is employed in general. That is, recording data are distributed to sectors in a certain unit of data size, and recording and reproduction are performed using the sectors as base units for rewriting. To the respective sectors as the base units for rewriting, addresses for identifying the sectors are added. Generally, the addresses are recorded as pits formed of concave and convex parts in an optical disk. A land/groove recording system has been employed commonly. In the system, track-guide grooves and inter-groove portions are used as areas for recording data in order to increase the density in a track direction.
A conventional optical disk having this sector configuration is described with reference to FIG. 12.
In FIG. 12(a), numeral 1001 indicates a substrate, numeral 1002 a recording film, numeral 1003 a first track, numeral 1004 a second track, numeral 1005 a sector of a divided portion of the track, numeral 1006 an address for identifying the sector, and numeral 1007 a data recording area for recording data. The first track 1003 is formed of a groove and the second track 1004 is formed of an inter-groove portion sandwiched by the groove of the first track. As shown in FIG. 12(a), the first track 1003 and the second track 1004 are configured to be positioned alternately on a one-revolution basis. Tracking by an optical beam is performed using the groove as a guide. However, the first track 1003 is in the groove and the second track 1004 is on the inter-groove portion, and therefore a tracking polarity is required to be inverted for the shift between the first track and the second track. As marks serving for detecting the polarity inversion, polarity inversion marks 1008 are provided in locations where the shift between the first track and the second track takes place. An optical disk device inverts the polarity in tracking using the polarity inversion marks 1008. In the sector 1005, the address 1006 and the data recording area 1007 are arranged as shown in FIG. 12(b).
Furthermore, as shown in FIG. 12(c), the address 1006 added for identifying the sector 1005 includes a sector mark 1009 indicating a sector starting point, a VFO mark 1010 used for generating a clock for the reproduction of the address part, an address mark 1011 for indicating the start of address data, a sector number 1012, a track number 1013, and an error detection code 1014. Since the sector mark 1009 and the address mark 1011 provide a data pattern for identifying the start of the address data, the data pattern is required to be a unique pattern that does not appear in the sector number 1012, the track number 1013, and the error detection code 1014. Therefore, the address data of the sector number 1012, the track number 1013, and the error detection code 1014 are recorded after being processed by bi-phase modulation or run-length-limiting modulation (RLL modulation). By this modulation process, a data pattern that does not appear from modulation rules for the other data can be obtained. Thus, a unique data pattern not in accordance with the modulation rules is used for the sector mark 1009 and the address mark 1011. The sector mark 1009 has a sufficient length to identify the start of the address area easily even when a PLL clock for synchronization is not locked.
As the modulation to the address data portion, the conventional example shown in FIG. 12 employs a bi-phase modulation in which xe2x80x9c0xe2x80x9d is modulated to be xe2x80x9c00xe2x80x9d or xe2x80x9c11xe2x80x9d, and xe2x80x9c1xe2x80x9d to be xe2x80x9c10xe2x80x9d or xe2x80x9c01xe2x80x9d. According to this modulation, a pattern with at least three xe2x80x9c1xe2x80x9d or xe2x80x9c0xe2x80x9d in a row is changed into a unique pattern not in accordance with the modulation rules. As the pattern not in accordance with the modulation rules, the conventional example shown in FIG. 12 employs xe2x80x9c10001110xe2x80x9d for the address mark 1011 and xe2x80x9c111111110000000xe2x80x9d for the sector mark 1009. A method of reproducing the address part in this conventional example is described briefly as follows.
Initially, the sector mark is detected. The sector mark has a unique pattern having eight xe2x80x9c1xe2x80x9d and eight xe2x80x9c0xe2x80x9d consecutively. When a mark with at least a certain length is detected using a free-running PLL clock, the sector mark 1009 can be detected easily. When this sector mark 1009 is detected, the PLL clock used for address demodulation is locked by the subsequent VFO 1010. After the lock of the PLL clock, the PLL clock determines xe2x80x9c1xe2x80x9d and xe2x80x9c0xe2x80x9d of the reproduced data, thus obtaining determination data. When the pattern ofxe2x80x9c10001110xe2x80x9d as the address mark 1011 is detected from the determination data, the subsequent data are identified as the sector number 1012, the track number 1013, and the error detection code 1014. In this way, the detection of the address mark 1011 allows the subsequent data to be identified as the sector number 1012, the track number 1013, and the error detection code 1014 that are to be demodulated. Thus, the data are demodulated.
In the above-mentioned conventional example, the address part 1006 includes the VFO mark 1010 for clock synchronization. However, a method in which the clock for demodulating address data is obtained by another means also has been practiced. This type of conventional example is described with reference to FIG. 13.
In FIG. 13(a), numeral 1101 indicates a substrate, numeral 1102 a recording film, numeral 1103 a track, numeral 1104 a sector of a divided portion of the track, numeral 1105 a segment of a divided portion of the sector, numeral 1106 an address for identifying the sector, and numeral 1107 a data recording area for recording data.
As shown in FIG. 13(b), in the leading location of the segment 1105, wobble pits 1108 used for obtaining a tracking signal and the subsequent clock pit 1109 for generating a clock for address and data demodulation are provided. As shown in FIG. 13(c), the address 1106 added to identify the sector 1104 includes an address mark 1110 for indicating the start of the address data, a sector number 1111, a track number 1112, and an error detection code 1113. As in the above-mentioned conventional example, the address mark 1110 has a unique pattern that does not appear in the sector number 1111, the track number 1112, and the error detection code 1113. Similarly in the conventional example shown in FIG. 13, the bi-phase modulation is employed for modulating the address data portion and xe2x80x9c10001110xe2x80x9d is used as the address mark 1110 as in the above-mentioned conventional example.
A method of reproducing the address part in this conventional example is described briefly as follows. Initially, the clock pit 1109 is detected. Using this clock pit, the frequency of a clock pit detection signal is multiplied by N using the PLL, thus generating a PLL clock for address demodulation. In the trailing part of the PLL clock, as in the above-mentioned conventional example, xe2x80x9c1xe2x80x9d and xe2x80x9c0xe2x80x9d of the reproduced data are determined, thus obtaining determination data. When the pattern of xe2x80x9c10001110xe2x80x9d as the address mark 1110 is detected from this determination data, the subsequent data are identified as the sector number 1111, the track number 1112, and the error detection code 1113. In this way, the detection of the address mark 1110 allows the subsequent data to be identified as the sector number 1111, the track number 1112, and the error detection code 1113 that are to be demodulated. Thus, the data are demodulated.
In a conventional optical disk, however, a unique pattern that does not appear in an address data portion has been required as an address mark to identify the starting position of an address. Therefore, recording was performed after the process of the data portion of the address by the bi-phase or RLL modulation. In a 1-7 modulation or 2-7 modulation as a type of bi-phase modulation or RLL modulation, one bit of address data becomes two bits or 1.5 bits after the modulation, thus increasing redundancy. Therefore, there has been a problem that the area required for the address data portion increases and thus the data recording area is reduced.
Moreover, in a conventional magneto-optical disk, in order to reproduce the first track and the second track continuously, a detection pit for tracking polarity inversion is provided, which also has been a factor that reduces the area in or from which data are recorded or reproduced. Furthermore, in the case of using one bit of the polarity inversion detection pit, it has been difficult to secure sufficient reliability with respect to defects of the disk and damages on the disk surface.
The present invention is intended to solve the aforementioned problems and to provide an optical disk in which the redundancy of an address part is reduced to enable high density information recording, and a tracking method using such an optical disk.
In order to achieve the above-mentioned object, a first disk-shaped storage medium according to the present invention includes a track divided into a plurality of areas and in the plurality of areas, address data are positioned. Error detection codes are added to data common to adjacent tracks of the address data for identifying the data common to adjacent tracks. According to this configuration, an effect can be obtained in that a synchronous process can be performed on data in address data reproduction without using a unique synchronization pattern.
In the first disk-shaped storage medium, it is preferable that the data common to adjacent tracks are positioned at a track pitch allowing the data common to adjacent tracks to be reproduced either on the track or in locations sandwiched by the track. This enables information useful for control to be read out from the optical disk without tracking control.
In order to achieve the above-mentioned object, a second disk-shaped storage medium according to the present invention has two tracks having different tracking polarities and being positioned alternately on a one-revolution basis. The tracks are divided into a plurality of areas and address data are positioned in the plurality of areas. Error detection codes are added to data common to adjacent tracks of the address data for identifying the data common to adjacent tracks. The data common to adjacent tracks include circumferential position information and are positioned at a track pitch allowing the data common to adjacent tracks to be reproduced either on the tracks or in locations sandwiched by the track. According to this configuration, the data common to adjacent tracks and the error detection codes for identifying the data common to adjacent tracks are read out without tracking control. Based on them, the switching of the tracking polarities can be detected.
In the first and second disk-shaped storage media, it is preferable that the address data are distributed to be positioned in the plurality of areas as one bit each. According to this, it is not necessary to accelerate a shift register storing the data common to adjacent tracks and the error detection codes identifying the data common to adjacent tracks in order to identify them in address data reproduction. Thus, the synchronous process to data can be performed easily.
In the second disk-shaped storage medium, it is preferable that the two tracks having different tracking polarities and being positioned alternately on a one-revolution are formed of tracks subjected to the tracking control by pairs of wobble marks positioned in locations in the plurality of areas into which the tracks are divided. The locations are shifted to the left and right with respect to the centers of the tracks and are spaced at a certain distance in a track-running direction. Respective positions of the wobble marks as a pair are changed alternately on the one-revolution basis. According to this, the tracking control is performed while the positions of the wobble marks, i.e. the polarities of tracking error signals are switched every revolution. Consequently, the track pitch can be reduced to increase the density of the tracks, while the one-spiral track configuration advantageous in continuously recording and reproducing mass data is maintained.
In order to achieve the above-mentioned object, a tracking method according to the present invention is characterized by the following. A disk-shaped storage medium is used. In the disk-shaped storage medium, two tracks with different tracking polarities are divided into a plurality of areas. Address data are positioned in parts of the plurality of areas. Error codes are added to data common to adjacent tracks of the address data for identifying the common data. The common data include circumferential position information and are positioned at a track pitch allowing the common data to be reproduced both on the tracks and between the tracks. Using this disk-shaped storage medium, starting points of the address data are detected based on the common data and the error detection codes. From the starting points, the circumferential position information is detected and the tracking polarities are determined from the position information. Thus, tracking control is performed. This method enables the switching of the tracking polarities to be detected easily.
In the first disk-shaped storage medium, it is preferable that pits producing the timings for demodulation of the address are positioned at a track pitch allowing the pits to be reproduced either on the track or in locations sandwiched by the track.
In order to achieve the above-mentioned object, an address reproduction method according to the present invention is characterized by the following. A disk-shaped storage medium is used. In the storage medium, a track formed of a groove and an inter-groove portion or of an inter-groove portion alone is divided into a plurality of areas. In the plurality of areas, address data are positioned. Using this storage medium, reference positions for producing the timings for demodulation of the address data are produced from the starting ends or the trailing ends of the grooves of the track divided into the plurality of areas.
In the first disk-shaped storage medium, it is preferable that the track is formed of a groove or an inter-groove portion and is divided into a plurality of areas and the address data are distributed to be positioned in the plurality of areas as one bit each at the positions of starting ends or trailing ends of the grooves divided into the plurality of areas.
In the first disk-shaped storage medium, it is preferable that the track is formed of a groove or an inter-groove portion and is divided into a plurality of areas and the address data are distributed to be positioned in the plurality of areas as one bit each at the positions of the starting ends of the grooves divided into the plurality of areas and the trailing ends of the grooves divided into the plurality of areas are aligned to be arranged at radially corresponding positions.
According to the above-mentioned configuration and methods, in order to identify the starting position of the address, it is not required to modulate the address data portion and to use a unique pattern obtained by the modulation rules as address marks. Therefore, the redundancy of the address part can be reduced considerably, thus achieving a high-density optical disk.
In the optical disk of the present invention, the positions where the tracking polarities are switched can be detected before a tracking pull-in operation. Therefore, in an optical disk with a track pitch providing a high-density track, a stable tracking pull-in operation can be performed.
Furthermore, the tracking control performed according to the signals from the wobble pits while recording and reproduction are performed only in groove portions enables the track pitch to be reduced and the difference in the recording/reproduction characteristics between tracks to be eliminated simultaneously.